Equipment and method to generate electricity by drawing high temperature geothermal

ABSTRACT

This invention is to give an applicable and effective equipment and method to generate electricity by drawing high temperature geothermal based on principle of heatpipe. It includes an evaporator ( 1 ), a condenser ( 2 ), a discharge valve ( 21 ), a vapor line ( 19 ), an electronically controlled throttle valve for gas ( 18 ), a main returning line ( 22 ), an electronically controlled throttle valve for liquid ( 23 ), an inter-returning line ( 24 ), a steam turbine ( 7 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the equipment of geothermal powergeneration. The invention particularly concerns an equipment and methodto generate electricity by using high temperature geothermal transferredto ground through continuous gas-liquid phase transition.

Description of Prior Developments

The geothermal resource is a new clean energy in the earth. It generallyrefers to the geothermal buried within 10 km depth of underground andhas the economic value of development and utilization under the currenttechnology. The geothermal with temperature lower than 150 C° is calledthe low-medium temperature geothermal, which can be used directly; whilethat higher than 150 C° is called the high temperature one, which mainlyis used to generate electricity. Based on the thermodynamics cycletheory, the higher temperature differential exists, the higher thermoefficiency happens.

Geothermal power generation refers to several modern scientific andtechnological domains, such as geology, earth physics, chemistry,drilling, materials science, power engineering, etc. Like the basicprinciple of other thermal power generation, based on the energytransfer, the geothermal power generation starts from transferring thegeothermal to the mechanical energy, then to the electricity. Currently,the underground thermal water and fry steam with temperature higher than200 C° is used to power generation. For the underground dry steam, itneeds to lead the dry steam from underground into the steam turbine towork, but the dry steam needs to be purified firstly. For theunderground hot water, it needs to use underground hot water to heatworking substances with low boiling point, such as chlorine ethane,Freon, to produce steam, and then leads the steam into the steam turbineto work, which is also known as the double cycle geothermal powergeneration. The FIG. 1 shows the principle scheme for the double cyclesystem of geothermal power generation, where the high temperatureunderground water (4) is drawn from the geothermal well (3) by the pump(5) and conducted into the evaporator (1) for purpose of heating. At theother aspect, the working substance with low boiling point (6) is led byworking substance pump (8) into another evaporator and is vaporized intothe high temperature steam, which comes into the steam turbine (7) togenerate power output (10). After then, the vaporized working substancebecomes the liquid again in the condenser (2). After heating the workingsubstance (6), the high temperature underground water (4) flows out ofthe evaporator (1) and back into ground through the water returningsystem (9).

For the geothermal power system mentioned above, it needs a large heattransfer area of evaporator (1) and condenser (2) due to the low heattransfer capacity of the low boiling working substances (6), whichincreases the manufacture cost and difficulty. The low boiling workingsubstances are of unstable, flammable, toxic, and prone to leak tocontaminate environment. In others, the water returning system, which isnecessary to prevent falling of water table and land subsidence,increase the cost of geothermal power exploitations and utilizations.Moreover, a lot of corrosive and scaling substances, such as hydrogensulfide, carbon dioxide, and other in the compound of the calciumcarbonate or silica, in the underground water and steam could severelycorrode the turbine, pipes and other equipments. All aspects mentionedabove adversely affect the geothermal power.

In short, the current geothermal power technology has the unfavorablefactors on high cost of construction and maintenance, low efficiency andreliability of working substances. To overcome those malpractices toutilize the geothermal power more efficiently, it needs to develop thenew simple, practical, low-cost, efficient, reliable and durableequipment and method.

To finish the purpose above, firstly, the traditional method drawingwater to the ground like in the FIG. 1 is banished. Instead, theevaporator (1) can be set underground and directly heated by the hightemperature geothermal. The working substance in the evaporator isvaporized into steam and is conducted into the turbine on ground throughan adiabatic pipe to work. After the condenser (2), the liquefiedworking substance is sent back to underground to vaporize. This loopcycle carries on continually. The principle of transferring heat toground using continuous gas-liquid phase transition of working substanceis classified as that of using heatpipe. This method has severalfavorable aspects. Firstly, its heat transfer efficiency is as a few tentimes as general metals, and it can conduct heat far with less heatlosing. In addition, it can modify the heat flux density by changingheating area. For example, it is possible to input heat with less heatarea, while output that with larger cooling area, vice versa. Theprinciple of heatpipe can be designed into several practical schemes inthe engineering applications. The FIG. 2, as the scheme on drawinghigh-temperature geothermal to power based on the principle of heatpipe,shows that the evaporator (1) is set at the bottom, where is the hightemperature zone, and is connected with the condenser (2) set upper onthe ground through the adiabatic vapor pipe (12) conducting vapor flow(13) and returning pipe (15) conducting liquid flow (14) of workingsubstance. When the heat source (11) is added to the evaporator (1), theliquid working substance is vaporized into high pressure vapor and flowsup toward the condenser (2) with low temperature and pressure. Theadiabatic connecting pipe (12,15) prevents the heat losing. In thecondenser (2), the working substance releases the latent heat (16) andcondenses into liquid. Since the condenser (2) is on upper, there is apressure head to make the liquid working substance automatically flowback to the evaporator (1) at bottom. The heat transfer on the phasechanging is carried out at the heat and cool ends and the process cankeep on and comes to a steady state if the added and released heat isequal. The principle, method and relative equipment shown in FIG. 2 issimple and practical, avoiding to pumping the geothermal water or steaminto any pipe equipment and reducing the construction and maintenancecost.

There are some technical problem required to solve for the applicationof this method. Firstly, it needs to use the high boiling point workingsubstances with high heat transfer coefficient, such as water, methanol,etc., to guarantee heat transfer capacity to make the evaporator volumeas small as possible. Secondly, those working substances being liquidunder normal temperature may form the vapor films under high environmenttemperature on the inner wall of the evaporator. A lot of vapor bubblesare formed on the wall replacing the liquid away from the wall, whichreduces the heat transfer capacity of heatpipe since the heat transfercoefficient of gas is much lower than that of liquid. This is why anyheatpipe works worse under high temperature. Besides that, both liquidand vapor flows in opposite directions. The shear force occurring at theliquid-vapor interfaces may inhibit some liquid back to the evaporator.When it occurs, a further increase in the heat input to the evaporatorleads to liquid droplets being entrained in the vapor flow and carriedto the condenser, eventually causing dry out of the evaporator. It canmake the equipment damaged.

SUMMARY OF THE INVENTION

The purpose of this invention is to give an applicable and effectiveequipment and method to generate electricity by drawing high temperaturegeothermal. The working principle is based on that of heatpipe. Theoriginality of this invention is that methodically directly drawing hightemperature geothermal through the evaporator located underground usingthe working substance with high heat transfer coefficient; structurallyrotating the two phase flows in the matched inter wall of the evaporatorthrough the inter-returning line to cancel the vapor film; directlyinserting the inter-returning line into the bottom of the evaporator toavoid the liquid droplet entrainment.

Those properties make the device work safely and reliably under hightemperature environment.

The Technical Scheme of the Invention

The FIG. 3, the schematics of about an equipment and method to generateelectricity by drawing high temperature geothermal according this toinvention, shows that It includes an evaporator (1), a condenser (2), adischarge valve (21), a vapor line (19), an electronically controlledthrottle valve for gas (18), a main returning line (22), anelectronically controlled throttle valve for liquid (23), aninter-returning line (24), a steam turbine (7); and

there is a vapor outlet and a liquid inlet on the top of the evaporator(1);

there is a vapor inlet and a vapor outlet on the steam turbine (7);

there is a vapor inlet and a liquid outlet on the condenser (2);

the vapor outlet on the evaporator (1) is connected with the vapor inleton the steam turbine (7) through a vapor connecting line (20), whichmakes the vapor come into the steam turbine (7);

an electronically controlled valve for gas (18) is installed in thevapor line (19) to adjust the vapor flow (13);

the vapor outlet on the steam turbine (7) is connected with the vaporinlet on the condenser (2), which makes the vapor come into thecondenser (2) after working in the steam turbine (7);

there is a discharge valve (21) in the upper of the condenser (2);

one end of a main returning line (22) is connected with the liquidoutlet of the condenser (2);

the other end of the main returning line (22) is connected with one endof an inter-returning line (24);

an electronically controlled valve for liquid (23) is installed in themain returning line (22) to control the liquid flow (14) into thecondenser (2);

the other end of the inter-returning line (24) is inserted from theliquid inlet up to the bottom of the evaporator (1).

The evaporator (1) is located underground zone with high temperaturegeothermal, while the condenser (2) and the steam turbine (7) are doneon the ground. The evaporator (1) is made of metal and cylinder- ortruncated right cone-shaped. The shape of the evaporator cavity istruncated conical or cylindrical. All the lines are covered with theadiabatic materials.

The liquefied working substance is conduct into the bottom of theevaporator (1) through the main returning line (22) and inter-returningline (24), which avoids the evaporator drying out due to the liquiddroplets entrainment that is caused by the shear force from the liquidand vapor flows in opposite directions.

The FIG. 4 describes the structure details of inter-returning line andevaporator presented in the FIG. 3. There are several rifling lines (25)on the inner surface and screw threads (26) on the outer surface of theinter-returning line (24) and the rotational directions of the riflinglines (25) and screw threads (26) are identical. Since the condenser (2)is higher than the evaporator (1) with a liquid head, the liquefiedworking substances flowing down in the inter-returning line (24) beginto rotate through the rifling lines (25) conduction. The liquid withsome momentum of inertia, coming into the evaporator cavity and beingvaporized gradually in the high temperature environment, becomes thevapor-liquid droplet two-phase flow (17). With the increasing of thepressure in the evaporator (1), the two-phase flows start torotationally move upward with the centrifugal force through theconduction of the screw threads (26) on the outer surface of theinter-returning line (24). Under high environment temperature, the vaporfilms generally form on the inner wall of the evaporator (1). A lot ofvapor bubbles are accumulated on the wall replacing the liquid away fromthe wall, which reduces the heat transfer capacity of the wall. However,the density of the liquid droplet is larger than that of vapor, theliquid droplets under the centrifugal force fly towards the wall of theevaporator (1) to smash the vapor bubbles and replace with liquid films.This movement recovers the heat transfer capacity of the wall of theevaporator (1) locally.

The FIG. 5 shows the force analysis of a liquid droplet on the wall ofthe evaporator with truncated right angle conical shape. It shows thatthe landing liquid droplet (29) on the inclined wall (27) takesresultant of forces (32) from gravity (28), wall reflection (30),results of (31) and centrifugal, centrifugal force (33) moves upward,which results the liquid film fully contacting to the heated wall, whichis good for the liquid film vaporized. The larger diameter of the upperof evaporator (1) with truncated right angle conical shape makes thecentrifugal force (33) less, which could make the flying liquid dropletscannot reach and cannot form the liquid film on the wall (27) of theevaporator (1). In this situation, the evaporator (1) with cylindricalshape has to be used to keep the centrifugal force. The selection ofdifferent shapes of the evaporator is based on the liquid head (heightdifferential) between the evaporator (1) and the condenser (2). For thelarge liquid head, it is better to use the truncated right angle conicalshape, since the large moment of inertial exists; while, on thecontrary, the cylindrical shape is better.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIG. 1 is the principle scheme for the double cycle system ofgeothermal power generation

The FIG. 2 is the scheme on drawing high-temperature geothermal to powerbased on the principle of heatpipe

The FIG. 3 is the schematics of about an equipment to produceelectricity by drawing high temperature geothermal according this toinvention

The FIG. 4 is the structure details of inter-returning line andevaporator

The FIG. 5 is the force analysis of a liquid droplet on the wall of theevaporator

The FIG. 6 is the schematics of an equipment to generate electricity bydrawing high temperature geothermal in the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principle and structure of the present invention will be moreparticularly described by an embodiment. The FIG. 6 is the schematics ofan equipment and method to generate electricity by drawing hightemperature geothermal in the embodiment according to this invention.

It includes an evaporator (1), a condenser (2), a discharge valve (21),a vapor line (19), an electronically controlled throttle valve for gas(18), a main returning line (22), an electronically controlled throttlevalve for liquid (23), an inter-returning line (24), a steam turbine(7).

Water, as the working substance with a large heat transfer coefficient,is atoxic, low cost and resourceful. The evaporator (1), condenser (2),and all connecting lines (19), (20), (22), (24) are made of the hightemperature resistant stainless steel, since it has a large heatconduction and has strong resistance to oxidation and deformation. Thelines (19) and (22) are covered with the adiabatic materials and putinto a protecting cover (34) with anti-corrosion and impact resistance.

There is a vapor outlet and a liquid inlet on the top of the evaporator(1); there is a vapor inlet and a vapor outlet on the steam turbine (7);there is a vapor inlet and a liquid outlet on the condenser (2); thevapor outlet on the evaporator (1) is connected with the vapor inlet onthe steam turbine (7) through a vapor connecting line (20), which makesthe vapor come into the steam turbine (7); an electronically controlledvalve for gas (18) is installed in the vapor line (19) to adjust thevapor flow (13); the vapor outlet on the steam turbine (7) is connectedwith the vapor inlet on the condenser (2), which makes the vapor comeinto the condenser (2) after working in the steam turbine (7); there isa discharge valve (21) in the upper of the condenser (2); one end of amain returning line (22) is connected with the liquid outlet of thecondenser (2); the other end of the main returning line (22) isconnected with one end of an inter-returning line (24); anelectronically controlled valve for liquid (23) is installed in the mainreturning line (22) to control the liquid flow (14) into the condenser(2); the other end of the inter-returning line (24) is inserted from theliquid inlet up to the bottom of the evaporator (1).

The evaporator (1) is located in the 2000-3000 meter deep in undergroundthermal water and fry steam with temperature higher than 200 C°. Thecondenser (2) and steam turbine (7) are located on the ground. The shapeof the evaporator cavity is truncated right angle conical.

The inter-returning line (24) is insert into the bottom of theevaporator (1), which avoids the evaporator (1) drying out due to theliquid droplets entrainment that is caused by the shear force from theliquid and vapor flows in opposite directions.

The FIG. 4 describes the structural details of inter-returning line inthe embodiment. There are 6 rifling lines (25) with 0.01 m deep on theinner surface and there are screw threads (26) with 0.01 m deep and thesame rotation direction on the outer surface of the inter-returning linewith 0.3 m outer diameter and 0.2 m inner diameter. Since the condenser(2) is 2000-3000 meter higher than the evaporator (1) with a liquidhead, the water flowing down in the inter-returning line (24) begins torotate through the rifling lines (25) conduction. The water with somemomentum of inertia, coming into the evaporator (1) and being vaporizedgradually in the high temperature environment, becomes the watervapor-droplet two-phase flow. With the increasing of the pressure in theevaporator (1), the two-phase flow starts to rotationally move upwardwith the centrifugal force through the conduction of the screw threads(26) on the outer surface of the inter-returning line (24). Somemomentum of inertia loss because of the friction and viscosity of thewater vapor-droplet two-phase flow.

The evaporator with the truncated right angle conical shape has thesloped wall. Referring the FIG. 5, where shows that the landing waterdroplet on the sloped wall taking resultant of forces moves upward toresult the water film fully contacting to the heated wall, which is goodfor the water film vaporized. The diameter of the upper of evaporator(1) with truncated right angle conical shape is 1 meter, the height ofit is 1.5 meter and the coning angle is 15°.

The water vapor with high temperature and high pressure comes into thesteam turbine (7) and pushes the rotor rotating to generate electricity(10). The condenser (2) releases the heat to change the water vapor toliquid water. Inside the condenser (2), there is a cooling system (35)based on cycling water. The cycling water absorbs the heat of the watervapor to make it reduce temperature of vapor to a liquid water state,which comes back into evaporator (1) again.

The present invention creates the equipment and method to generateelectricity by using high temperature geothermal transferred to groundthrough continuous gas-liquid phase transition based on principle ofheatpipe. Particularly, directly locate the evaporator in undergroundgeothermal, use water as working substance, and design uniquecomponents, which makes the equipment work in highly thermal efficient,structurally simple, low costly, and reliable.

1. An equipment and method to generate electricity by drawing high temperature geothermal includes an evaporator (1), a condenser (2), a discharge valve (21), a vapor line (19), an electronically controlled throttle valve for gas (18), a main returning line (22), an electronically controlled throttle valve for liquid (23), an inter-returning line (24), a steam turbine (7); and there is a vapor outlet and a liquid inlet on the top of the evaporator (1); there is a vapor inlet and a vapor outlet on the steam turbine (7); there is a vapor inlet and a liquid outlet on the condenser (2); the vapor outlet on the evaporator (1) is connected with the vapor inlet on the steam turbine (7) through a vapor connecting line (20), which makes the vapor come into the steam turbine (7); an electronically controlled valve for gas (18) is installed in the vapor line (19) to adjust the vapor flow (13); the vapor outlet on the steam turbine (7) is connected with the vapor inlet on the condenser (2), which makes the vapor come into the condenser (2) after working in the steam turbine (7); there is a discharge valve (21) in the upper of the condenser (2); one end of a main returning line (22) is connected with the liquid outlet of the condenser (2); the other end of the main returning line (22) is connected with one end of an inter-returning line (24); an electronically controlled valve for liquid (23) is installed in the main returning line (22) to control the liquid flow (14) into the condenser (2); the other end of the inter-returning line (24) is inserted from the liquid inlet up to the bottom of the evaporator (1).
 2. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said evaporator (1) is made of metal and cylinder- or truncated right cone-shaped and is located underground zone with high temperature geothermal.
 3. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said condenser (2) and steam turbine (7) are done on the ground.
 4. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said the lines (19), (22) and (24)are covered with the adiabatic materials.
 5. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said inter-returning line (24) is insert into the bottom of the evaporator (1).
 6. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said inter-returning line (24) bears with several rifling lines (25) on the inner surface and screw threads (26) on the outer surface, and the rotational directions of the rifling lines (25) and screw threads (26) are identical. 